The present disclosure relates to patient support apparatuses, such as hospital beds or stretchers, and particularly to patient support apparatuses having powered transport devices such as motorized wheels or motorized traction drives to propel the patient support apparatus along a floor. More particularly, the present disclosure relates to user interfaces and control systems for such transport devices.
Some patient support apparatuses, such as hospital beds or stretchers, have powered transport devices that propel the patient support apparatus along a floor. See, for example, U.S. Pat. Nos. 7,090,041; 7,083,012; 7,021,407; 7,011,172; 7,007,765; 6,902,019; 6,877,572; 6,772,850; 6,752,224; 6,749,034; 6,725,956; 6,588,523; 6,390,213; 6,330,926; and 5,083,625. It is common for such devices to have controllers that are programmed to sense a plurality of conditions before a motor will be activated to propel the patient support apparatus along a floor. For example, such devices usually sense whether or not casters are braked, whether or not an enable switch or other safety switch is engaged by a user, whether or not a battery has sufficient power to activate the motor, and whether or not an AC power plug of the patient support apparatus is plugged into an electrical outlet. If the caster brakes are set, if the enable switch is not engaged, if the battery power is too low, or if the AC power plug is plugged in, the powered transport devices will typically be disabled from propelling the associated patient support apparatus.
Most of the known prior art transport devices of hospital beds and stretchers are configured to propel the bed only in forward and reverse directions. Such prior art transport devices usually include some type of electrical input device, such as a potentiometer or a load cell with a strain gage output, for providing a signal that controls the speed at which the bed or stretcher is propelled. These electrical input devices are generally infinitely adjustable between upper and lower limits to provide for an infinite number of speed settings between upper and lower limits. However, these electrical input devices are relatively expensive and it can sometimes be difficult for users to apply a consistent force to a load cell, through a handle or other structure, especially when there is a tendency for the bed or stretcher to drive away from the user after application of the initial driving force by the user, or to keep a potentiometer rotated to a consistent position given the fact that such devices are usually biased toward a neutral position in which the powered transport device is not activated. Thus, in such patient support apparatuses, the powered transport may feel “jerky” to the users and to any patients on the patient support apparatuses.
It has also been proposed to have a powered transport device that will allow the wheel or traction drive to be re-oriented relative to the patient support apparatus to allow for side-to-side or lateral transport in addition to forward and reverse transport. See, for example, PCT Publication No. WO 2006/059200 A2. Having traction drives that can propel a patient support apparatus forwardly, rearwardly, and side-to-side introduces additional complexities that need to be dealt with in connection with user interfaces and control algorithms of such transport devices.